Catalytic conversion of fluorocarbons



United States Patent This invention relates to a method of preparing organic fluorine-containing compounds and, more particularly to a method of preparing unsaturated fluorocarhons from saturated fluorine-containing organic compounds.

Processes for the conversion of saturated fluorine-containing compounds into unsaturated fluorocarbons are known in the art. Some of the known methods, which involve pyrolysis or a reaction with hydrogen at pyrolysis temperatures, usually involve high reaction temperatures, long contact times, low product yield and low conversions and are, accordingly, less than desirable. Still other processes, utilizing low temperature techniques, almost invariably require the use of expensive reagents and, accordingly, have not been commercially feasible.

Compounds containing large amounts of fluorine are extremely valuable for a variety of reasons. For example, tetrafiuoroethylene and hexafluoropropylene are quite valuable as intermediates for the synthesis of high molecular Weight polymers which have many industrial applications. Other fluorocarbons, such as perfluorocyclobutene, are useful as chemical intermediates, solvents, aerosol propellants, hydraulic fluids and dielectric media. Accordingly, there is a well-defined need in the art for new processes for the synthesis of such fluorocarbons which eliminate as many of the inherent deficiencies of the conventional prior art processes as .possible.

The present invention overcomes many of the problems associated with prior art processes such as described above by providing novel catalytic materials in the presence of which the reaction is carried out. More specifically, the present invention resides in the carrying out of the fluorocarbon synthesis in question in the presence of crystalline aluminosilicate zeolite catalysts.

Zeolitic materials, 'both natural and synthetic, in naturally occurring and modified forms, have been demonstrated in the past to have catalytic capabilities for various types of hydrocarbon conversion. Such Zeolitic materials are ordered crystalline aluminosilicates having a definite crystalline structure Within which there are passages, pores or cavities of definite ranges of size. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as molecular sieves and are utilized in a variety of ways to take advantage of these properties. The present invention, as aforesaid, involves the use of such zeolitic materials for the purpose of converting saturated fluorinecontaining organic compounds to unsaturated fluorocarbons.

It is accordingly a primary object of the present invention to provide a novel fluorocarbon conversion process involving the use of crystalline aluminosilicate zeolite catalysts.

It is a still iurther object of the present invention to provide a novel fluorocarbon conversion process involving the use of crystalline aluminosilicates having a Zeolitic structure of rigid three-dimensional network, uniform 3,337,645 Patented Aug. 22, 1967 pore size and well-defined intra-crystalline dimensions such that only reactant or product molecules of suitable size and shape may be transported in either direction between the exterior phase and the interior of the crystalline zeolite.

It is another important object of the present invention to provide a novel process for forming perfluoroolefins comprising pyrolyzing a fluorine-containing compound in the presence of a crystalline aluminosilicate zeolite catalyst to form either CF or CF (CF ),,CF= fragments, which recombine to provide the perfluoroolefin desired.

It is still another important object of the present invention to provide a novel catalytic process for synthesizing perfluoroolefins comprising contacting a fluorine-containing compound under reaction conditions with a crystalline aluminosilicate zeolite catalyst, said fluorine-containing compound having the formula where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF wherein n is any whole number including zero.

These and other objects and advantages of the present invention will become more apparent upon reference to the ensuing description and appended claims.

The objects of the present invention are accomplished by contacting with a molecular sieve zeolite catalyst, under reaction conditions, a halo-carbon of the structure:

where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF where n is any whole number including zero. While n maybe any value, the preferred values of n are 1 or 2. Examples of a variety of starting materials coming within the framework of the above formula include chlorodifluoromethane; dichlorodifluoromethane; l-chloro 1 hydroperfluoroethane; 1 dichloroperfluoropropane; 1-dichloroperfluoroethane; etc. Preferred reactants are the simple fluorocarbons such as Cl CF and ClHCF both of which will yield on pyrolysis the extremely useful CFFCF It is postulated that the mechanism involved in the synthesis of the present invention involves the pyrolysis of the fluorine-containing starting material to form CF or CF (CF ),,CF= divalent fragments (11: being any whole number including zero) which then recombine to form the desired perfluoroolefin.

The aluminosilicates useable as catalysts in accordance with the present invention include a wide variety of positive ioncontaining crystalline aluminosilicates, both natural and synthetic. These aluminosilicates can be described as a rigid three-dimensional network of $0., and A10 .tet-rahedra in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal or an alkaline earth metal cation. This equilibrium can be expressed by formula wherein the ratio of A1 to the number of the various cations, such as Ca, Sr, Na K or Li is equal to unity. One cation may be exchanged either in entirety or partially by another cation utilizing ion exchange techniques as discussed hereinbelow. By means of such cation exchange, it is possible to vary the size of the pores in the given aluminosilicate by suitable selection of the particular cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.

A description of zeolites of the type useable in the present invention is found in Patent 2,971,824, whose disclosure is hereby incorporated herein by reference. These aluminosilicates have well-defined infra-crystalline dimensions such that only reactant or product molecules of suitable size and shape may be transported in either direction between the exterior phase and the interior of the crystalline zeolite.

In their hydrated form, the aluminosilicates may be represented by the formula:

M O:A1 0 :wSlOz:yHz0

wherein M is a cation which balances the electrovalence of the tetrahedra, n represents the valence of the cation, w the moles of SiO and y the moles of H 0, the removal of which produces the characteristic open network system. The cation may be any one or more of a number of positive ions as aforesaid, such ions being discussed in greater detail hereinafter. The parent zeolite is dehydrated to actuate it for use as a catalyst. Although the proportions of inorganic oxides in the silicates and their spatial arrangement may vary, effecting distinct properties in the aluminosilicates, the main characteristic of these materials is their ability to undergo dehydration without substantially affecting the SiO., and A framework. In this respect, this characteristic is essential for obtaining catalyst compositions of high activity in accordance with the invention.

Representative materials include a synthetic faujasite, designated Zeolite X, which can be represented in terms of mole ratios of oxides as follows:

wherein M is a metal cation having a valence of not more than three, n represents the valence of M, and y is a value up to eight depending on the identity of M and degree of hydration of the crystal. The sodium form may be represented in terms of mole ratios of oxides as follows:

0.9 Na O:Al O :2.5 SiO :6.1 H 0 (111) Another synthesized crystalline aluminosilicate, designated Zeolite A, can be represented in mole ratios of oxides as:

wherein M represents a metal cation, n is the valence of M, and y is any value up to about 6. As usually prepared, Zeolite A contains primarily sodium cations and is designated sodium Zeolite A.

Other suitable synthesized crystalline aluminosilicates are those designated Zeolite Y, L and D.

The formula for Zeolite Y (which is a synthetic faujasite) expressed in oxide mole ratios is:

0.9:02 Na O:Al O :wSiO :yH O (V) wherein w is a value ranging from 3 to 6 and y may be any value up to about 9.

The composition of Zeolite L in oxide mole ratios may be represented as:

l.0;l:0.1M O:AlzOa26.4:|:O.5SlO2IyHzO wherein M designates a metal cation, n represents the valence of M, and y is any value from 0 to 7.

The formula for Zeolite D, in terms of oxide mole ratios, may be represented as:

0.9:02 [xNa O: (1-x) K 0] :Al O wSiO :yH O (VII) wherein x is a value of 0 to 1, w is from 4.5 to about 4.9 and y, in the fully hydrated form, is about 7.

Other synthetic crystalline aluminosilicates which can be used include those designated as Zeolites R, S, T, Z, E, P, Q and B.

The formula for Zeolite R in terms of oxide mole ratios may be written as follows:

0.9:02 Na O:Al O :wSiO :yH O (VIII) wherein w is from 2.45 to 3. 65, and y, in the hydrated form, is about 7.

The formula for Zeolite S in terms of oxide mole ratios may be written as:

wherein w is from 4.6 to 5.9 and y, in the hydrated form, is about 6 to 7.

The formula for Zeolite T in terms of oxide mole ratios may be written as:

wherein x is any value from about 0.1 to about 0.8 and y is any value from about 0 to about 8.

The formula for Zeolite Z in terms of oxide mole ratios may be written as:

K20 :A1203 I wherein y is any value not exceeding 3.

The formula for Zeolite E in terms of oxide mole ratios may be written as:

0.9:|:0.1M2 O:AlzO :l.95d;0.1SiOq:yH O

wherein M is a metal cation, n is the valence of the cation, and y is a value of 0 to 4.

The formula for Zeolite F in terms of oxide mole ratios may be written as:

0.95;l;0.15M O:AlzO :2.05;l;O.3SiO1:yH O

E (XIII) wherein M is a metal cation, n is the valence of the cation, and y is any value from 0 to about 3.

The formula for Zeolite Q, expressed in terms of oxide mole ratios, may be written as:

0.95i0.05M 0IAl2O3Z2.2:l:0.05siO2ZyHg0 E (XIV) wherein M is a metal cation, n is the valence of the cation, and y is any value from 0 to 5.

The formula for Zeolite B may be written in terms of oxide mole ratios as:

1.O:l;0.2M O:Al O;:3.5i1.5SlOa:yH:O

ii xv wherein M represents a metal cat-ion, n is the valence of the cation, and y has an average value of 5.1 but may range from 0 to 6.

Other synthesized crystalline aluminosilicates include those designated as ZK4 and ZK5.

ZK4 can be represented in terms of mole ratios of oxides as:

0.1 to 0.33:0.7 to 1.0M 0:A1,o3:2.5 to 495103 71110 (XII) tains primarily sodium cations and can be represented by unit cell formula:

7.5:2 Na:2i0.5 Hz9i2 AlO zl5i2 SiO (XVII) The major lines of the X-ray diffraction pattern of ZK-4 are set forth in Table 1 below:

TABLE 1' d value of reflection in A. 100 I/I 12.00 100 9.12 29 8.578 2.. 73 7.035 52 6.358 15 5.426 23 4.262 11 4.062 49 3.662 65 3.391 30 3.254 41 2.950 54 2.725 10 2.663 7 2.593 15 2.481 2 2.435 1 2.341 2 2.225 2 2.159 4 2.121 5 2.085 2 2.061 2 2.033 5 1.90 2 1.880 2 1.828 1 1.813 1 1.759 1 1.735 1 1.720 5 1.703 1 1.669 2 1.610 1 1.581 2 1.559 1 ZK-4 can be prepared by preparing an aqueous solution of oxides containing Na O, A1 SiO H 0 and tetramethyl-ammonium ion having a composition, in terms of oxide mole ratios, which falls within the follow- Nao ROI-194N120 maintaining the mixture at a temperature of about 100 C. to 120 C. until the crystals are formed, and separating the crystals from the mother liquor. The crystal material is thereafter washed until the wash etfiuent has a pH essentially that of wash water and subsequently dried.

ZK-S is representative of another crystalline aluminosilicate which is prepared in the same manner as Zeolite ZK-4 except that N,N-dimethyltriethylenediammonium hydoxide is used in placed of tetramethylammonium hydroxide. ZK-5 may be prepared from an aqueous sodium aluminosilicate mixture having the following composition expressed in terms of oxide mole ratios as:

MM Na o 2) 0 2 3) 21 a2 2) 6N2(CH3) zl Si0 The N,N'-dimethyltriethylenediamrnonium hydroxide used in preparing ZK-S can be prepared by methylating 1,4-diazabicyclo-(2.2.2)-octane with methyl iodide or dimethyl sulfate, followed by conversion to the hydroxide by treatment with silver oxide or barium hydroxide. The reaction may be illustrated as follows:

N I ogogou 2CH3I (XVIII) In using the N,N'-dimethyltriethylenediammonium hydroxide compound in the preparation of ZK-5, the hydroxide may be employed per se, or further treated with a source of silica, such as silica gel, and thereafter reacted with aqueous sodium aluminate in a reaction mixture whose chemical composition corresponds to the above-noted oxide mole ratios. Upon heating at temperatures of about 200 to 600 C., the methyl ammonium ion is converted to hydrogen ion.

Quite obviously, the above-listed molecular sieves are only representative of the synthetic crystalline aluminosilicate molecular sieve catalysts Which may be used in accordance with the process of the present invention, the particular enumeration of such sieves not being intended to be exclusive.

At the present time, two commercially available molecular sieves are those of the A series and of the X series. A synthetic Zeolite known as Molecular Sieve 4A is a crystalline sodium aluminosilicate having an effective pore diameter of about 4 angstroms. In the hydrated form, this material is chemically characterized by the formula:

The synthetic Zeolite known as Molecular Sieve 5A is a crystalline aluminosilicate salt having an effective pore diameter of about 5 angstroms and in which substantially all of the 12 ions of sodium in the immediately above formula are replaced by calcium, it being understood that calcium replaces sodium in the ratio of one calcium ion for two sodium ions. A crystalline sodium aluminosilicate is also available commercially under the name of Mo- I lecular Sieve 13X. The letter X is used to distinguish before activation by dehydration, the 13X material contains water and has the unit cell formula The synthetic zeolite known as Molecular Sieve 10X is a crystalline aluminosilicate salt in which a substantial proportion of the sodium ions of the 13X material have been replaced by calcium.

Among the naturally occurring crystalline aluminosilicates which can be employed for purposes of the invention, the preferred aluminosilicates are those which sorb hydrocarbons above C Exemplary of such aluminosilicates are faujasite, heulandite, clinoptilolite, dachiardite, and aluminosilicates represented as follows:

Chabazite Na O-Al O -4SiO -6H O. Gmelinite Na -Al O -4SiO -6H O. Mordenitc Na O-Al O Other aluminosilicates which can be used are those resulting from caustic treatment of various clays.

Of the clay materials, montmorillonite and kaolin families are representative types which include the subbentonites, such as bentonite, and the kaolins commonly identified as Dixie, McNamee, Georgia and Florida clays in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays may be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification. In order to render the clays suitable for use, however, the clay material is treated with sodium hydroxide or potassium hydroxide, preferably in admixture with a source of silica, such as sand, silica gel or sodium silicate, and calcined at temperatures ranging from 230 F. to 1600 F. Following calcination, the fused material is crushed, dispersed in water and digested in the resulting alkaline solution. During the digestion, materials with varying degrees ofcrystallinity are crystallized out of solution. The solid material is separated from the alkaline material and thereafter washed and dried. The treatment can be effected by reacting mixtures falling within the following weight ratios:

Na O/clay (dry basis) 1.0-6.6 to 1 SiO /clay (dry basis) 0.013.7 to 1 H O/Na O (mole ratio) 35-180to1 Molecular sieves are ordinarily prepared initially in the sodium form of the crystal. The sodium ions in such form may, as desired, be exchanged for other cations, as will be described in greater detail below. In general, the process of preparation involves heating, in aqueous solution, an appropriate mixture of oxides, or of materials whose chemical composition can be completely represented as a mixture of oxides Na O, A1 0 SiO and H 0 at a temperature of approximately 100 C. for periods of 15 minutes to 90 hours or more. The product which crystallizes within this hot mixture is separated therefrom and water washed until the water in equilibrium with the zeolite has a pH in the range of 9 to 12. After activating by heating until dehydration is attained, the substance is ready for use.

For example, in the preparation of sodium zeolite A, suitable reagents for the source of silica include silica sol, silica gel, silicic acid or sodium silicate. Alumina can be supplied by utilizing activated alumina, gamma alumina, alpha alumina, aluminum trihydrate or sodium aluminate. Sodium hydroxide is suitably used as the source of the sodium ion and in addition contributes to the regulation of the pH. All reagents are preferably soluble in water. The reaction solution has a composition, expressed as mixtures of oxides, within the following ranges: SiO /Al O of 0.5 to 2.5, Na O/SiO of 0.8 to 3.0 and H O/Na O of 35 to 200. A convenient and generally employed process of preparation involves preparing an aqueous solution of sodium aluminate and sodium hydroxide and then adding with stirring an aqueous solution of sodium silicate.

The reaction mixture is placed in a suitable vessel which is closed to the atmosphere in order to avoid losses of water and the reagents are then heated for an appropriate length of time. Adequate time must be used to allow for recrystallization of the first amorphous precipitate that forms. While satisfactory crystallization may be obtained at temperatures from 21 C. to 150 C., the pressure being atmospheric or less, corresponding to the equilibrium of the vapor pressure with the mixture at the reaction temperature, crystallization is ordinarily carried out at about C. As soon as the zeolite crystals are completely formed they retain their structure and it is not essential to maintain the temperature of the reaction any longer in order to obtain a maximum yield of crystals.

After formation, the crystalline zeolite is separated from the mother liquor, usually by filtration. The crystalline mass is then washed, preferably with salt-free water, while on the filter, until the wash water, in equilibrium with the zeolite, reaches a pH of 9 to 12. The crystals are then dried at a temperature between 25 C. and C. Activation is attained upon dehydration, as for example at 350 C. and 1 mm. pressure or at 350 C. in a stream of dry air.

It is to be noted that the material first formed on mixing the reactants is an amorphous precipitate which is, generally speaking, not catalytically active in the process of the invention. It is only after transformation of the amorphous precipitate to crystalline form that the highly active catalyst described herein is obtained.

Molecular sieves of the other series may be prepared in a similar manner, the composition of the reaction mixture being varied to obtain the desired ratios of ingredients for the particular sieve in question.

The molecular sieve catalysts useable in the process of the present invention may be in the sodium form as aforesaid or may contain other cations, including other metallic cations and/or hydrogen. In preparing the non-sodium forms of the catalyst composition, the aluminosilicate can be contacted with a non-aqueous or aqueous fluid medium comprising a gas, polar solvent or water solution containing the desired positive ion. Where the aluminosilicate is to contain metal cations, the metal cations may be introduced by means of a salt soluble in the fluid medium. When the aluminosilicate is to contain hydrogen ions, such hydrogen ions may be introduced by means of a hydrogen ion-containing fluid medium or a fluid medium containing ammonium ions capable of conversion to hydrogen ions.

In those cases in which the aluminosilicate is to contain both metal cations and hydrogen ions, the aluminosilicate may be treated with a fluid medium containing both the metal salt and hydrogen ions or ammonium ions capable of conversion to hydrogen ions. Alternatively, the aluminosilicate can be first contacted with a fluid medium containing a hydrogen ion or ammonium ion capable of conversion to a hydrogen ion and then with a fluid medium containing at least one metallic salt. Similarly, the aluminosilicate can be first contacted with a fluid medium containing at least one metallic salt and then with a fluid medium containing a hydrogen ion or an ion capabllle of conversion to a hydrogen ion or a mixture of bot Water is the preferred medium for reasons of economy and ease of preparation in large scale operations involving continuous or batchwise treatment. Similarly, for this reason, organic solvents are less preferred but can be employed providing the solvent permits ionization of the acid, ammonium compound and metallic salt. Typical solvents include cyclic and acyclic ethers such as dioxane, tetrahydrofuran, ethyl ether, diethyl ether, diisopropyl ether, and the like; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate, propyl acetate; alcohols such as ethanol, propanol, butanol, etc.; and

9 miscellaneous solvents such as dimethylformamide, and the like.

The hydrogen ion, metal cation or ammonium ion may be present in the fluid medium in an amount varying within wide limits dependent upon the pH value of the fluid medium. Where the aluminosilicate material has a molar ratio of silica to alumina greater than about 5.0, the fluid medium may contain a hydrogen ion, metal cation, ammonium ion, or a mixture thereof, equivalent to a pH value ranging from less than 1.0 up to a pH value of about 10.0. Within these limits, pH values for fluid media containing a metallic cation and/ or an ammonium ion range from 4.0 to 10.0, and are preferably "between a pH value of 4.5 to 8.5. For fluid media containing a hydrogen ion alone or with a metallic cation, the pH values range from less than 1.0 up to about 7.0 and are preferably within the range of less than 3.0 up to 6.0.

-Where the molar ratio of the aluminosilicate is greater than about 3.0 and less than about 5.0, the pH value for the fluid media containing a hydrogen ion or a metal cation ranges from 3.8 to 8.5. Where ammonium ions are employed, either alone or in combination with metallic cations, the pH value ranges from 4.5 to 9.5 and is preferably within the limit of 4.5 to 8.5. When the aluminosilicate material has a molar ratio of silica to alumina less than about 3.0, the preferred medium is a fluid medium containing an ammonium ion instead of a hydrogen ion. Thus, depending upon the silica to alumina ratio, the pH value varies within rather Wide limits.

In carrying out the treatment With the fluid medium, the procedure employed comprises contacting the aluminosilicate with the desired fluid medium or media until such time as metallic cations originally present in the aluminosilicate are removed to the desired extent. Repeated use of fresh solutions of the entering ion is of value to secure more complete exchange. Effective treatment with the fluid medium to obtain a modified aluminosilicate having high catalytic activity will vary, of course, with the duration of the treatment and temperature at which it is carried out. Elevated temperatures tend to hasten the speed of treatment whereas the duration there of varies inversely with the concentration of the ions in the fluid medium. In general, the temperatures employed range from below ambient room temperature of 24 C. up to temperatures below the decomposition temperature of the aluminosilicate. Following the fluid treatment, the treated aluminosilicate is washed with water, preferably distilled water, until the efiluent wash water has a pH value of wash Water, i.e., between about and 8. The aluminosilicate material is thereafter analyzed for metallic ion content by methods well known in the art. Analysis also involves analyzing the effluent wash for anions obtained in the wash as a result of the treatment, as well as determination of and correction for anions that pass into the effluent wash from soluble substances or decomposition products of insoluble substances which are otherwise present in the aluminosilicate as impurities. The aluminosilicate is then dried and dehydrated.

The actual procedure employed for carrying out the fluid treatment of the aluminosilicate may be accomplished in a batchwise or continuous method under atmospheric, subatmospheric or superatrnospheric pressure. A solution of the ions of positive valence in the form of a molten material, vapor, aqueous or non-aqueous solution, may be passed slowly through a fixed bed of the aluminosilicate. If desired, hydrothermal treatment or a corresponding non-aqueous treatment with polar solvents may be effected by introducing the aluminosilicate and fluid medium into a closed vessel maintained under autogenous pressure. Similarly, treatments involving fusion or vapor phase contact may be employed providing the melting point or vaporization temperature of the acid or ammonium compound is below the decomposition temperature of the aluminosilicate.

A wide variety of acidic compounds can be employed with facility as a source of hydrogen ions and include both inorganic and organic acids.

Representative inorganic acids which can be employed include acids such as hydrochloric acid, hypochlorous acid, chloroplatinic acid, sulfuric acid, sulfurous acid, hydrosulfuric acid, peroxydisulfonic acid (H S O peroxymonosulfuric acid (H dithionic acid (H S O sulfamic acid (H NHS H), amidodisulfonic acid chlorosulfuric acid, thiocyanic acid, hyposulfurous acid (H S O pyrosulfuric acid (H S O thiosulfuric acid (T1 8 0 nitrosulfonic acid (HSO .NO), hydroxylamine disulfonic acid [(HSO NOH], nitric acid, nitrous acid, hyponitrous acid, carbonic acid and the like.

Typical organic acids which find utility in the practice of the invention include the monocarboxylic, dicarboxylic and polycarboxylic acids which can be aliphatic, aromatic or cycloaliphatic in nature.

Representative aliphatic monocarboxylic, dicarboxylic and polycarboxylic acids include the saturated and unsaturated, substituted and unsubstituted acids, such as formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, propiouic acid, Z-bromopropionic acid, 3-bromopropionic acid, lactic acid, n-butyric acid, isobutyric acid, crotonic acid, n-valeric acid, isovaleric acid, n-caproic acid, oenanthic acid, pelargonic acid, capric acid, undecyclic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkylsuccinic acid, alkenylsuccinic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutonic acid, muconic acid, ethylidene malonic acid, isopropylidene malonic acid, allyl malonic acid.

Representative aromatic and cycloaliphatic monocarboxylic, dicarboxylic and polycarboxylic acids include 1,2- cyclohexanedicarboxylic acid, l,4-cyclohexanedicarboxylic acid, 2-carboxy-ZZ-methylcyclohexaneacetic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,8-naphthalenedicarboxylic acid, l,2-naphthalenedicarboxylic acid, tetrahydrophthalic acid, 3-carboxy-cinnamic acid, hydrocinnamic acid, pyrogallic acid, benzoic acid, ortho, meta and para-methyl, hydroxy, chloro, bromo and nitro-substituted benzoic acids, phenylacetic acid, mandelic acid, benzylic acid, hippuric acid, benzenesulfonic acid, toluenesulfonic acid, methanesulfonic acid and the like.

Other sources of hydrogen ions include carboxy polyesters prepared by the reaction of an excess of polycarboxylic acid or an anhydride thereof and a polyhydric alcohol to provide pendant carboxyl groups.

Still other materials capable of providing hydrogen ions are ion exchange resins having exchangeable hydrogen ions attached to base resins comprising cross-linked resinous polymers of monovinyl aromatic monomers and polyvinyl compounds. These resins are well known materials which are generally prepared by copolymerizing in the presence of a polymerization catalyst one or more monovinyl aromatic compounds, such as styrene, vinyl toluene, vinyl xylene, with one or more divinyl aromatic compounds such as divinyl benzene, divinyl toluene, divinyl xylene, divinyl naphthalene and divinyl acetylene. Following copolymerization, the resins are further treated with suitable acids to provide the hydrogen form of the resin.

Still another class of compounds which can be employed are ammonium compounds which decompose to provide hydrogen ions when an aluminosilicate treated with a solution of said ammonium compound is subjected to temperatures below the decomposition temperature of the alumino-silicate. l

Representative ammonium compounds which can be employed include ammonium chloride, ammonium bromide, ammonium iodide, ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium sulfide, ammonium thiocyanate, ammonium dithiocarbamate, am-

monium peroxysulfate, ammonium acetate, ammonium tungstate, ammonium molybdate, ammonium benzoate, ammonium borate, ammonium carbamate, ammonium sesquicarbonate, ammonium chloroplumbate, ammonium citrate, ammonium dithionate, ammonium fluoride, ammonium gallate, ammonium nitrate, ammonium nitrite, ammonium formate, ammonium propionate, ammonium butyrate, ammonium valerate, ammonium lactate, ammonium malonate, ammonium oxalate, ammonium palmitate, ammonium tartrate and the like. Still other ammonium compounds which can be employed include complex ammonium compounds such as tetramethylammonium hydroxide, trimethylammonium chloride. Other compounds which can be employed are nitrogen bases such as the salts of guanidine, pyridine, quinoline, etc.

A wide variety of metallic compounds can be employed with facility as a source of metallic cations and include both inorganic and organic salts of the metals of Groups 113 through VIII of the Periodic Table, with the metals of Groups IB, IIB, IVA and VII being preferred. Of the latter, the metals of Group IIB produce the most desirable results.

Representative of the salts which can be employed include chlorides, bromides, iodides, carbonates, bicarbonates, sulfates, sulfides, thiocyanates, dithiocarbamates, peroxysulfates, acetates, benzoates, citrates, fluorides, nitrates, nitrites, formates, propionates, butyrates, valerates, lactates, malonates, oxalates, palmitates, hydroxides, tartrates and the like. The only limitation on the particular metal salt or salts employed is that it be soluble in the fiuid medium in which it is used. The preferred salts are the chlorides, nitrates, acetates and sulfates.

Rare earth salts may be advantageously employed. Such salts can either be the salt of a single metal or, preferably, of mixtures of metals such as a rare earth chloride or didymium chlorides. As hereinafter referred to, a rare earth chloride solution is a mixture of rare earth chlorides consisting essentially of the chlorides of lanthanum, cerium, neodymium and praseodymium with minor amounts of samarium, gadolinium and yttrium. The rare earth chloride solution is commercially available and it contains the chlorides of a rare earth mixture having the relative composition: cerium (as CeO 48% by weight; lanthanum (as La O 24% by weight; praseodymium (as Pr O by weight; neodymium (as Nd O 17% by weight; samarium (as Sm O 3% by weight; gadolinium (as Gd O 2% by weight; yttrium (as Y O 0.2% by weight; and other rare earth oxides 0.8% by weight. Dydmium chloride is also a mixture of rare earth chlorides, but having a low cerium content. It consists of the following rare earths determined as oxides: lanthanum, 45-46% by weight; cerium, 12% by weight; praseodymium, 910% by weight; neodymium, 32-33% by weight; samarium, 56% by weight; gadolinium, 34% by weight; yttrium, 0.4% by weight; other rare earths, 12% by weight. It is to be understood that other mixtures of rare earths are equally applicable in the instant invention.

Representative metal salts which can be employed, aside from the mixture mentioned above, include silver chloride, silver sulfate, silver nitrate, silver acetate, silver arsinate, silver bromide, silver citrate, silver carbonate, silver oxide, silver tartrate, calcium acetate, calcium arsenate, calcium benzoate, calcium bromide, calcium carbonate, calcium chloride, calcium citrate, beryllium bromide, beryllium carbonate, beryllium hydroxide, beryllium sulfate, barium acetate, barium bromide, barium carbonate, barium citrate, barium malonate, barium nitrite, barium oxide, barium sulfide, magnesium chloride, magnesium bromide, magnesium sulfate, magnesium sulfide, magnesium acetate, magnesium formate, magnesium stearate, magnesium tartrate, manganese chloride, manganese sulfate, manganese acetate, manganese carbonate, manganese formate, zinc sulfate, zinc nitrate, zinc acetate, zinc chloride, zinc bromide, aluminum chloride, aluminum bromide, aluminum acetate, aluminum citrate, aluminum nitrate, aluminum oxide, aluminum phosphate, aluminum sulfate, titanium bromide, titanium chloride, titanium nitrate, titanium sulfate, zirconium chloride, zirconium nitrate, zirconium sulfate, chromic acetate, chromic chloride, chromic nitrate, chromic sulfate, ferric chloride, ferric bromide, ferric acetate, ferrous chloride, ferrous arsenate, ferrous lactate, ferrous sulfate, nickel chloride, nickel bromide, cerous acetate, cerous bromide, cerous carbonate, cerous chloride, cerous iodide, cerous sulfate, cerous sulfide, lanthanum chloride, lanthanum bromide, lanthanum nitrate, lanthanum sulfate, lanthanum sulfide, yttrium bromate, yttrium bromide, yttrium chloride, yttrium nitrate, yttrium sulfate, samarium acetate, samarium chloride, samarium bromide, samarium sulfate, neodymium chloride, neodymium oxide, neodymium sulfide, neodymium sulfate, praseodymium chloride, praseodymium bromide, praseodymium sulfate, praseodymium sulfide, selenium chloride, selenium bromide, tellurium chloride, tellurium bromide, etc.

The aluminosilicate catalysts useable in connection with the process of the present invention may be used in powdered, granular or molded state formed into spheres or pellets of finely divided particles having a particle size of 2 to 500 mesh. In cases where the catalyst is molded, such as by extrusion, the aluminosilicate may be extruded before drying, or dried or partially dried and then extruded. The catalyst product is then preferably precalcined in an inert atmosphere near the temperature contemplated for conversion but may be calcined initially during use in the conversion process. Generally, the aluminosilicate is dried between 150 F. and 600 F. and thereafter calcined in air or an inert atmosphere of nitrogen, hydrogen, helium, flue gas or other inert gas at temperatures ranging from about 500 F. to 1500 F. for periods of time ranging from 1 to 48 hours or more.

The aluminosilicate catalysts prepared in the foregoing manner may be used as catalysts per se or as intermediates in the preparation of further modified contact masses consisting of inert and/or catalytically active materials which otherwise serve as a base, support, carrier, binder, matrix or promoter for the aluminosilicate. One embodiment of the invention is the use of the finely divided aluminosilicate catalyst particles in a siliceous gel matrix wherein the catalyst is present in such proportions that the resulting product contains about 2 to by weight, preferably about 5 to 50% by weight, of the aluminosilicate in the final composite.

The aluminosilicate-siliceous gel compositions can be prepared by several methods wherein the aluminosilicate is combined with silica while the latter is in a hydrous state such as in the form of a hydrosol, hydrogel, wet gelatinous precipitate or a mixture thereof. Thus, silica gel formed by hydrolyzing a basic solution of alkali metal silicate with an acid such as hydrochloric, sulfuric, etc., can be mixed directly with finely divided aluminosilicate having a particle size less than 40 microns, preferably within the range of 2 to 7 microns. The mixing of the two components can be accomplished in any desired manner, such as in a ball mill or other types of kneading mills. Similarly, the aluminosilicate may be dispersed in a hydrosol obtained by reacting an alkali metal silicate with an acid or an alkaline coagulant. The hydrosol is then permitted to set in mass to a hydrogel which is thereafter dried and broken into pieces of desired shape, or dispersed through a nozzle into a bath of oil or other water-immiscible suspending medium to obtain spheroidally shaped bead particles of catalyst. The aluminosilicate siliceous gel thus obtained is washed free of soluble salts and thereafter dried and/ or calcined as desired.

The siliceous gel matrix may also consist of a plural gel comprising a predominant amount of silica with one or more metals or oxides thereof. The preparation of plural gels is well known and generally involves either separate precipitation or coprecipitation techniques in which a suitable salt of the metal oxide is added to an alkali metal 13 silicate and an acid or base, as required, is added to precipitate the corresponding oxides. The silica content of the siliceous gel matrix contemplated herein is generally with the range of 55 to 100 weight percent with the metal oxide content ranging from zero to 45 percent. Minor 14 The desired end products may ordinarily be separated from by-products by ordinary distillation techniques.

The following examples will serve to illustrate the process of the present invention:

. Exam le 1 amounts of promoters or other materials which may be p a I a e e 0 I present in the composition include cerium, chrominum, A 20 X VYCOF reactor 18 Packed Wlih Of a cobalt, tungsten, uranium, platinum, lead, zinc, calcium, zinc exchanged 13X Molecular Sieve and heated to 400 magnesium, lithium, silver, nickel and their compounds. Gaseous chlofodlfluol'omethane 1S Passed 0V6! U16 The aluminosilicate catalyst may also be incorporated u) catalyst at a rate Of 0.2 fL /hI. The resultant gas phase in an alumina gel matrix conveniently prepared by addp t contams the following materials: ing ammonium hydroxide, ammonium carbonate, etc. to

1 f 1 h 1 hl 1 Percent a sat o a umilnurn, suc as aummurn c on e, aumi- CCIHFZ (unreacted) 70 .num sulfate, aluminum nltrate, etc., 1n an amount to CFaH 4 form aluminum hydroxide, which, upon drying, is con- CHZFZ g 5 verted to alumina. The aluminosilicate catalyst can be CFaCl M 4 mixed with the dried alumina or combined while the F W z-c z l2 alumlna 1s 1n the form of a hydrosol, hydrogel or wet other gases 5 gelatinous precipitate. T"

For maximum effectiveness in carrying out the process other examples 113mg VaFlOuS Infilal exchanged 13X of the present invention, the crystalline aluminosilicate Molecular SleVe Catalysts are Set forth 111 the follOWing used as a catalyst for converting the starting saturated table:

TABLE I Example Catalyst Reactant Ftfi/hr. Temp, C. Conv., Yield, Percent Yield, Percent Yield, Percent I Gas Percent g= F2 CFi Other Products Pb 13X 001m 0. 2 500 14 88 3 9 Zn 13X 001m 0. 2 600 60 80 2 18 Cd 13X 001m 0. 2 500 45 85 s 12 Cd 13X 001m 0. 2 600 65 82 4 14 Cu 13X 001m 0. 2 400 3 90 2 8 Cu 13X 001m 0. 2 500 18 88 4 8 Na 13X 001m 0. 2 500 1 50 50 Ni 13X 001m 0. 2 500 5 90 5 10 oo 13X CClzFz 0. 2 500 5 88 2 5 Zn 13X CHCIF, 0. 2 500 20 90 5 5 Zn 13X CHCIF; 0. 2 600 90 85 5 10 fluorocarbon to the perfluoroolefin should have pores or channels of a size such that the reactant will pass into such pores or channels and the reaction products will be removable therefrom. Quite obviously, the particular pore size which is desirable will vary depending upon the particular starting materials utilized and the products to be formed as a result of the pyrolysis process. In general, however, it can be stated that the most desirable molecular sieves for use in the instant process are those having a pore size of about 5-15 angstrom units.

The process of the present invention is preferably carried out on a continuous basis in a reactor containing a fixed bed or layer of the molecular sieve catalyst through which the charge stock is passed under the desired conditions of temperature and pressure. If desired, of course, a continuous process using a fluidized bed may also be employed in a conventional manner.

The reaction conditions employed in the process of the present invention will necessarily vary depending upon the starting material employed. In general, short contact times are preferred, a flow rate of about 5-100 ml./min. of charge stock for a catalyst bed of about 5-10 ml. being particularly satisfactory. It should be noted notwithstanding this preferred flow rate that higher flow rates may be employed if desired.

Normally, the reaction is carried out at atmospheric pressure, though subatmospheric pressures may be employed with advantage since the reaction generally yields two molecules for each one molecule of reactant. Temperatures employed are preferably about 300-600 C with a preferred range being about 400-600 C.

In general when the halomethane starting material yields free chlorine as a by-product of the reaction, a small amount of a hydrocarbon gas such as methane is added to remove the chlorine by reaction.

By-product formation may be minimized through the use of an inert atmosphere. Towards this end, gaseous nitrogen, hydrogen, carbon monoxide, carbon dioxide or the like could be added to the reactant stream.

In the foregoing portion of the specification, a novel process for pyrolyzing saturated fluorocarbons to form perfluoroolefins in the presence of crystalline aluminosilicate zeolite catalysts has been set forth. It is to be understood, however, that the process of the present invention is also applicable to the use in said process of isomorphs of said crystalline aluminosilicates. For example, the aluminum may be replaced by elements such as gallium and silicon by elements such as germanium.

The invention may be embodied in other specific forms without departing from the spirit or essential character- Where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF wherein n is any whole number from 0-2.

2. A process as defined in claim 1 wherein said catalyst contains a plurality of uniform interstitial pores and the diameter of said pores is such as to permit entry therein and egress therefrom of the respective fluorine-containing starting compound and the perfluoroolefin reaction product.

3. A process as defined in claim 1 wherein said catalyst 15 contains a pluarlity of uniform interstitial pores and the diameter of said pores is at least about A.

4. A process as defined in claim 1 wherein said synthesis is carried out at a temperature of about 300600 C.

5. A process for converting a saturated fluorinated compound to a fluorine-containing unsaturate comprising contacting said saturated fluorinated compound under conversion conditions with a crystalline aluminosilicate zeolite catalyst; said saturated fluorinated compound having the formula A IHLF where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF wherein n is any whole number including zero.

6. A method of converting dichlorodifluoromethane to tetrafluoroethylene and other products comprising pyrolyzing said dichlorodifluoromethane in the presence of a crystalline aluminosilicate zeolite catalyst.

7. A method of converting chlorodifiuoromethane to tetrafluoroethylene and other products comprising pyrolyzing said chlorodifluoromethane in the presence of a crystalline aluminosilicate zeolite catalyst.

8. A process for converting a saturated fluorinated compound to a fluorine-containing unsaturated compound comprising pyrolyzing said saturated fluorinated compound at a temperature of about 300-600 C. with a crystalline aluminosilicate zeolite catalyst; said saturated fluorinated compound having the formula 16 where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF wherein n is any whole number from 0-2.

9. A process of synthesizing perfluoroolefins comprising pyrolyzing a fluorine-containing compound at a temperature of at least about 300 C. sufliciently to form divalent fragments selected from the group consisting of CF and CF (CF CF= wherein n is any whole number including zero; said pyrolysis taking place in the pres ence of a crystalline aluminosilicate zeolite catalyst.

10. A process as defined in claim 9 wherein said di valent fragments recombine to form perfluoroolefins.

11. A process as defined in claim 10 wherein said fluorine-containing compound has the formula where A is selected from the group consisting of H, Cl, Br and I; X is selected from the group consisting of Cl, Br and I; and R is selected from the group consisting of F and CF (CF wherein n is any whole number from 0-2.

References Cited UNITED STATES PATENTS 3,140,253 7/1964 Plank et al. 208

FOREIGN PATENTS 917,093 1/ 1963 Great Britain. 1,068,695 11/1959 Germany.

LEON ZITVER, Primary Examiner.

DANIEL D. HORWITZ, Examiner. 

1. A PROCESS FOR SYNTHESIZING PERFLUOROOLEFINS COMPRISING PYROLYZING A FLUORINE-CONTAINING COMPOUND IN THE PRESENCE OF A CRYSTALLINE ALUMINOSILICATE ZEOLITE CATALYST; SAID FLUORINE-CONTAINING COMPOUND HAVING THE FORMULA 